Reactive mixtures of thermoplastic vinyl chloride polymers with reactive plasticizers

ABSTRACT

REACTIVE MIXTURES OF PASTY CONSISTENCY ARE FORMED BY MIXING THERMOPLASTIC POLYVINYL CHLORIDE PARTICLES WITH REACTIVE PLASTICIZERS SUCH AS A MIXTURE OF ETHYLENE GLYCOL DIMETHACRYLATE AND STYRENE AND FREE-RADICAL GENERATING CATALYST. POWDERED FOR FIBROUS FILLERS ARE DESIRABLY ADDED. ESPECIALLY IF THE MIXTURE IS INITIALLY FLUID. THESE PLASTICIZERS ARE ABSORBED OR ADSORBED INTO THE POLYVINYL CHLORIDE AND THE PROPORTIONS OF PLASTICIZER AND FILLER IS ADJUSTED TO PROVIDE THE DESIRED PASTY MIXTURE. THIS MIXTURE MAY BE CONVERTED TO AN INTERMEDIATE GEL STATE BY HEATING AT A TEMPERATURE AND FOR A TIME INTERVAL, WHICH DOES NOT CAUSE SIGNIFICANT POYMERIZATION. THE GEL PRODUCT IS A FLEXIBLE SOLID WHICH CAN BE CURED AT TEMPERATURES OF 120-200*C. IN PREFERRED PRACTICE, MIXTURE OF DISPERSION GRADE AND SUSPENSION GRADE POLYVINYL CHLORIDE PARTICLES ARE USED TO FORM AN INITIALLY FLUID MIXTURE AND FIBERS ARE MIXED, AND IF NECESSARY THE MIXTURE IS ALLOWED THE THICKEN, TO FORM A NON-FLOWABLE PASTE WHICH IS ENCASED IN PROTECTIVE CELLOPHANE SHEETS AND ROLLED TO SHEET FROM ESSENTIALLY FREE FROM AIR WITH THE RESIN AND FIBERS FLOWING TOGETHER TO MAINTAIN UNIFORM DISTRIBUTION. THIS SHEETED MATERIAL CAN BE GELLED TO STABILIZE IT FOR SUBSEQUENT USE.

United States Patent 3,557,049 REACTIVE MIXTURES OF THERMOPLASTIC VINYLCHLORIDE POLYMERS WITH REAC- TIVE PLASTICIZERS Irving E. Muskat, Miami,Fla., assignor to C-J Corporation, a corporation of Delaware No Drawing.Continuation-impart of applications Ser. No. 573,858, Aug. 22, 1966, andSer. No. 656,349, July 27, 1967. This application Sept. 17, 1968, Ser.No. 760,363

Int. Cl. C08f /28 U.S. Cl. 260-41 21 Claims ABSTRACT OF THE DISCLOSUREReactive mixtures of pasty consistency are formed by mixingthermoplastic polyvinyl chloride particles with reactive plasticizerssuch as a mixture of ethylene glycol dimethacrylate and styrene andfree-radical generating catalyst. Powdered or fibrous fillers aredesirably added, especially if the mixture is initially fluid. Theseplasticizers are absorbed or adsorbed into the polyvinyl chloride andthe proportions of plasticizer and filler is adjusted to provide thedesired pasty mixture. This mixture may be converted to an intermediategel state by heating at a temperature and for a time interval, whichdoes not cause significant polymerization. The gel product is a flexiblesolid which can be cured at temperatures of 120-200 C. In preferredpractice, a mixture of dispersion grade and suspension grade polyvinylchloride particles are used to form an initially fluid mixture andfibers are mixed in, and if necessary the mixture is allowed to thicken,to form a non-flowable paste which is encased in protective cellophanesheets and rolled to sheet form essentially free from air with the resinand fibers flowing together to maintain uniform distribution. Thissheeted material can be gelled to stabilize it for subsequent use.

The present invention is a continuation-in-part of my prior applicationsSer. Nos. 573,858, filed Aug. 22, 1966, and 656,349, filed July 27,1967.

The present invention relates to the production of plastic productsbased on thermoplastic polyvinyl chloride polymers and copolymers andwhich possess thermoset properties characterized by increased heatdistortion temperature and solvent resistance. The invention is particularly directed to the provision of non-porous products which can bestored for long periods and which, nonetheless, are rapidly curable bythe mere application of heat and pressure to form cured products ofimproved properties. The invention especially contemplates pastymixtures containing powdered and/or fibrous fillers in which the fillerand resin components flow together under applied pressure as when theproduct is rolled or pressed into a sheet or molded in order to formreinforced products in which the reinforcement is uniformly distributed.The mixtures of the invention including the sheeted products noted abovecan be converted into an intermediate gel condition in which the mixturehas the character of a flexible solid which is stable on storage andreadily molded and cured under applied heat and pressure.

The handling of vinyl chloride polymers has presented considerabledifliculty and the present invention is concerned with minimizing thesedifficulties as well as upgrading the chemical and physical propertiesof the products which are produced. The production of struc turalelements by high speed molding processes is particularly contemplatedsince the hand lay up procedures and pre-form molding required withpolyester and epoxyice type resins have not been satisfactory eitherfrom the standpoint of economy or from the standpoint of quality.

In accordance with the invention, particles of a thermoplastic vinylchloride polymer are combined with liquid plasticizer comprising a lowmolecular weight polyester reaction product of alpha,beta-ethylenicallyunsaturated monocarboxylic acid and a monoethylenic monomer from thegroup of styrene, vinyl toluene, chlorostyrene and similar monovinylaromatic compounds and mixtures thereof. The materials and proportionsare selected to provide a pasty mixture in which any fillers areuniformly dispersed. In addition to any desired reinforcement,freeradical polymerization catalyst as well as whatever stabilizers,modifiers, dyes, colorants and other usual polyvinyl chloride additiveswhich are desired are dissolved or dispersed in the mixture before thepaste is processed further. This pasty mixture can be molded directly orit can be extruded or sheeted with or without gelation at a temperatureand for a time interval which does not cause significant polymerization,the pasty form of the mixture enabling all of the components of themixture to flow together under pressure. The pasty mixture can also beconverted to an intermediate gel state in which the product is aflexible solid while still subject to forming, drawing, shaping andmolding at elevated temperature which converts the gel to a curedproduct having thermoset characteristics. The gel can be stored and usedin sheet form or it can be pellitized or sliced into moldable materialsto be fed into mold cavities or used in diverse molding processes.

Conversion to the gel state is achieved by subjecting the mixture to anintermediate solvating temperature for a time sufficient to cause theliquid plasticizers to flux with the vinyl chloride polymer withoutcausing significant polymerization. In this way, a largely non-porousflexible solid is produced in which the capacity for polymerization attemperatures above 120 C. to induce thermosetting characteristics isretained for long periods of time. The intermediate temperatures neededfor solvation are generally above C., with temperatures of from 80 C.l20C. being effective when applied for periods of from about /2 to about 5minutes. Below 80 C. longer time is needed. At temperatures above 120C., e.g., temperatures of from l35l50 C., gelation will occur in from515 seconds. It is to be understood that the temperatures referred toare press temperatures and, particularly at the higher temperatures, itdoes not appear that the mixture actually reaches this temperature. Thisintermediate non-porous polymerizable flexible solid is termed a gel andit is preferably used in the form of a sheet, or the sheet may be slicedinto discrete moldable pieces which facilitates subsequent use. Despitethe solid condition of the gel, it flows under heat and pressure and thediscrete pieces fuse together to form a unitary non-porous product.

The desired pasty condition is preferably obtained by utilizing mixturesof dispersion grade resin particles and suspension grade resinparticles. The term pasty is used herein to define a thixotropic-likecondition which is non-flowable in the absence of applied pressure.

The thermoplastic vinyl chloride polymers which are used should containat least about by weight of vinyl chloride, more preferably at least butthe balance of the polymer may be constituted by other polymerizableethylenic monomers such as vinyl acetate, vinylidene chloride and thelike. Polyvinyl chloride containing in excess of 96% by weight of vinylchloride is particularly preferred. Polyvinyl chloride made by anyprocess can be reduced to a desirable particle size and used in thisinvention, but it is stressed that preferred practice uses suspensiongrade particles in admixture with dispersion grade particles since thisenables fluid systems to be fiber reinforced and then sheeted with ahigher percentage of polyvinyl chloride.

While polyvinyl chloride of high molecular weight tends to provideproducts of outstanding properties, nonetheless, products of lowermolecular weight and copolymers containing a small proportion ofcopolymerizing monomer such as vinyl acetate or vinylidene chloride areat times desirable due to greater ease of handling.

Materials and proportions are selected to provide a pasty mixture whichcan be handled so that, when it is subjected to pressure, it will flowwith all of the intermixed components flowing together to remain inuniform admixture.

Generally speaking, up to about 50 parts of liquid plasticizers can bemixed with 50 parts of polyvinyl chloride resin to obtain an effectivefluid or pasty composition and this will occur when dispersion graderesins are mixed with plasticizer mixtures rich in styrene and wherereinforcing materials are incorporated. It is generally preferred to usesmaller proportions of liquid plasticizer sufficient to obtain a fluidor pasty blend for a long enough time to permit the mixture to besheeted and gelled if desired.

The preferred mixtures are initially fluid which permits fibers andother reinforcements to be mixed when desired. Usually the final mixtureincluding all the fillers, fibers and additives as well as the polyvinylchloride and plasticizers becomes pasty and grease-like eitherimmediately after admixture or shortly thereafter when some of theplasticizers are absorbed by the solids in the mixture, and this pastycharacteristic markedly improves the sheeting operation. The ability ofresin and filler to move in unison not only insures uniformity, but itavoids damaging discrete fibers and it prevents entrapment of air in themixture.

The invention includes the concept of blending the reinforcing materialswith the liquid components of the mixture before the resin particles areadded so that mixtures can be prepared at very high vinyl chloride resincontent and with good wetting of the fillers.

Similarly, and with initially fluid mixtures, the invention contemplatesincreasing the proportion of vinyl chloride resin and of the reinforcingmaterial if any is used by evaporating away some of the volatilemonoethylenic monomer, especially styrene, after the fluid mixture hasbeen worked to uniformly distribute the components of the mixture or toincorporate reinforcing fibers therein.

Removal of volatile monomer when desired is particularly contemplatedafter the mixture has been converted to the gel state. When theprotective cellophane sheets are removed, unpolymerized volatile monomerwill evaporate from the flexible solid gel at room temperature.Vaporization can be accelerated using moderate heat and vacuum and, solong as the temperature is not excessive or maintained for too long atime, the gel will not cure. When the desired proportion of styrene hasbeen removed, the gel product or discrete pieces thereof are maintainedin a closed container to minimize further loss of monomer therefrom. Thevaporized monomer can be recovered in conventional fashion if desired.

Generally, the ratio of plasticizer to vinyl chloride resin should be atleast about 30/70 to provide an initially fluid mixture, but thisminimum will vary with the proportion of suspension grade resin.Preferably, a ratio of at least 35/65 is used with at least 25% of theresin being of suspension grade to insure adequate fluidity and workingtime to incorporate large proportions of solid materials, preferably atleast 5%, based on total weight of reinforcing fibers. Most preferably,from 40-65% of the resin is suspension grade resin with the balancebeing dispersion grade resin since these mixtures thicken to provide ahighly tacky mixture in which the resin and solids incorporated thereinfiow together as the mixture is sheeted out with rolling pressure.

The sheeting referred to is usually carried out by rolling the tackymixture between sheets of cellophane, thus removing entrapped air.Nitrocellulose coated cellophane is helpful to minimize adhesion betweenthe confining sheet and the resin and permits easy heat sealing of thecellophane sheets. Of course, other films and metal foils which areinert to the various components of the mixture can also be used.

When the proportion of dispersion grade resin is excessive, theproportion of plasticizer needed for initial fluidity and adequateworking time is excessive. Conversely, with too much suspension resin,adequate tack is not achieved.

It is stressed that the prior art used liquid mixtures of resin andplasticizer and this required dispersion grade resins and excessiveproportions of plasticizer to provide a stable plastisol which was thenused to reinforce fabrics of various type by impregnation. The thrust ofthe present invention is completely opposite to these standardtechniques.

It is also pointed out that prior efforts to incorporate discrete fibershave involved milling of the resin-fiber mixture which disrupts andfractures the fiber component of the mixture.

The liquid plasticizer in this invention is a mixture of monoethylenicand polyethylenic monomers, both being essential to obtain aninexpensive system which will be adequately fluid for fiberreinforcement, and adequately reactive and compatible to permit thedevelopment of adequate cure.

While styrene, vinyl toluene, chlorostyrene and similar monovinylaromatic compounds and mixtures thereof are all useful to provide thebulk of the monoethylenic plasticizer since all are adequately fiuid,reactive, absorptive in polyvinyl chloride and compatible in polymericform both with the polyvinyl chloride and with polyethylenic monomers,styrene and vinyl toluene are preferred. The cost advantage of thesemonomers is combined in the invention With the fluidity and furthereconomy achieved by the selection of suspension grade polyvinyl chlorideand also with economy in production. The chlorostyrenes generally givelonger pot-life, and when necessary, this characteristic justifies theiruse.

Vinyl toluene is particularly appropriate and the vpresence of aproportion of this monomer is advantageous in providing an increase inmixing time and, despite its loW cost, it possesses low volatility, lowheat of polymerization and better shrinkage properties, all of whichlead to superior product properties. Thus, a proportion of vinyl toluenemay be desirably included When styrene is the monomer and vinyl tolueneis especially valuable for the production of superior low cost productshaving the properties noted hereinbefore. Indeed, the use of styrene inadmixture with a less volatile monovinyl aromatic monomer such as vinyltoluene or chlorostyrene is particularly appropriate to permit higherproportions of solid material (polyvinyl chloride or powdered or fibrousfiller) to be used. The lower cost styrene which is more volatile willevaporate preferentially from the gel product containing the same, andthe more expensive and superior monomer remains behind to participate inthe final cure.

From the standpoint of overall properties including reactivity,cross-linking capacity for monovinyl aromatic compounds, andcompatibility with monovinyl aromatic compound and polyvinyl chloride inboth monomeric and polymeric form, the invention employs as thepolyethylenic plasticizer a low molecular weight polyester reactionproduct of alpha, beta-unsaturated monocarboxylic acid such as acrylicacid, chloroacrylic acid, bromoacrylic acid, alkoxy acrylic acid(methoxy or butoxy), alkyl, aryl or acyl acrylic acid (methacrylic acid,phenylacrylic acid, and crotonic acid) with an aliphatic polyhydricalcohol such as ethylene glycol, propylene glycol, n-butylene glycol,isobutylene glycol, 1,3-butylene glycol, 1,5-pentane Typical reactiveplasticizers in accordance with the invention are exemplified byethylene glycoldimethacrylate, propylene glycol dimethacrylate,diethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate,1,5-pentane diol dimethacrylate and trimethylol propane trimethacrylate.Similarly, the acrylate and chloroacrylate and other a-substitutedacrylic acid esters may be used.

Less preferably, unsaturated alcohol esters of unsaturated carboxylicacids such as allyl acrylate or methacrylate or methallyl acrylate ormethacrylate may also be used.

The reactive plasticizer is preferably a liquid at room temperature orgives a liquid solution when mixed with the monoethylenic plasticizercomponent so that fluid mixtures can be easily handled. 1,3-butyleneglycol dimethacrylate is especially preferred and will be used toillustrate the invention.

From the standpoint of proportions, the monoethylenic plasticizer mayconstitute from 20% to 98% of the liquid plasticizer component butpreferably the proportion of monoethylenic plasticizer is from 4095% byweight. On the other hand, at least a portion of the mixture ofplasticizers must be polyethylenic if a significant thermosetting cureis to be achieved.

It should be understood that certain features of this invention havesignificance even when the solvent resistance conferred by thepolyethylenic plasticizer is not regarded as important, and in suchinstance, this compo nent can be omitted. On the other hand, it ispossible to omit the monoethylenic plasticizer, though, as a practicalmatter, increase in the proportion of polyethylenic plasticizer above50% based on total unsaturated plasticizer provides limited furtherimprovement in solvent resistance.

Fiber reinforcement is a feature of the invention, for it is fiberreinforcement which underscores the physical properties of the productwhich are exceptional even in the absence of fiber reinforcement.Indeed, and especially when a mineral fiber such as glass fiber is used,the achievement of uniform distribution of a sizable proportion of fibercan greatly enhance properties which are not normally regarded asphysical, e.g., the heat resistance of the product can be significantlyimproved by the mere fact of appropriate fiber reinforcement. Glassfiber is generally available as strands made up of many fibers-usually50-250 or more fibers in each strand. These strands of glass fibers arecoated, and it is important (for best reinforcing properties) that thecoating is one which permits defibrillation of the strand and goodwetting of the fibers with the resin component.

At least by weight of fiber based on plasticized resin should be presentin order to significantly upgrade the properties of the resin component.On the other hand, larger proportions of fiber are desirably worked intothe fluid mixtures which are formulated, preferably at least by weight.Even larger proportions of fiber can be worked in, e.g., up to about50%, but more usually from 1030%. As will be appreciated, the proportionwhich can be worked into the liquid mixture will depend upon the initialfluidity of the mixture, the rate at which the mixture thickens, thefineness of the fiber, and its length.

Fibers up to about 1" in length are well tolerated and fibers having alength of /s" to /2 are particularly desirable. On the other hand,longer fibers may be used though these will likely be broken up to someextent because of working and/or comminution of the gelled mixture intodiscrete pieces. Also, the fiber can be broken up to powder form (milledfibers) before incorporation but it will still retain its fibrouscharacter so that it will function in a manner superior to ordinaryparticulate pigments and fillers which are also useful in the invention,although such powder-sized fibers will not entirely substitute forfibers of Vs and longer which are far more easily used in this inventionthan heretofore.

It will be appreciated that dyes, lubricants, stabilizers, inhibitorsand small proportions of standard polyvinyl chloride plasticizers ifdesired and other conventional additives may also be used as isgenerally known in the industry.

While special techniques are needed for efficient incorporation ofreinforcing material and especially fiber reinforcement, any mixingtechnique such as milling or extrusion can be used when disruption ofthe fibers as a result of the shearing forces encountered is not ofsignificance or where reinforcing fibers are not present. The mixturesof the invention are desirably sheeted and then gelled and thisintermediate product having the form of a flexible solid gel is thenused as such or may be desirably sliced into discrete pieces tofacilitate handling and use. These discrete pieces will normally possessdimensions in the range of A3" to 1". It is a feature of the inventionthat these discrete pieces of gelled material will flow together underpressure at a temperature in excess of about C. and polymerization canthen take place to provide an integral and unitary cured mass.Moreover,if the pieces contain reinforcing fibers, these fibers will flow withthe resin component of the piece so that the final cured product can bereinforced as desired. The pieces of gelled material are desirablystored in closed containers to maintain the proportion of volatilemonomer therein constant.

The final cure requires temperatures above about 120 C. at whichpolymerization of the plasticizers takes place and a thermosetting cureensues rapidly, normally completed in from 1 to 6 minutes. Temperaturesup to about 200 C. can be practicably used for the cure. Ifpolyfunctional plasticizer is used alone, or with chlorostyrene as themonofunctional monomer, cure can occur at a lower temperature and can beeffected in shorter time.

It is not feasible to catalyze the mixtures of the invention aftergelation and the catalyst is preferably added to one or more of theliquid components before the solid components of the mixture are added.It has been found that ordinary free-radical polymerization catalystscan be used and that these will retain their activity despite elevatedtemperature gelling and subsequent prolonged storage. Moreover, theflexible solid gels which are formed as taught herein will respond toappropriate curing temperatures with extensive flow of resin and fiberas well as extensive cure.

The catalysts which are used in the invention are freeradicalpolymerization catalysts, usually of the peroxy type. Numerous catalystsof this type are well-known, specific catalyst selection in accordancewith the invention being of secondary significance. These catalystsretain activity for long periods in the solid flexible mass which isformed. Catalyst selection is primarily determined by the temperature atwhich the catalyst liberates freeradicals in sufficient quantity in areasonable time. Thus, any catalyst known to be useful for curing theplasticizer per se can be used to cure the combinations which areformulated because effective solvation of these mixtures can occur belowthe temperatures which will cause extensive curing. Generally, thepreferred catalysts liberate free-radicals in the range of from 120-200C. On this basis, t-butyl perbenzoate is preferred to benzoyl peroxidewhen higher temperature cure is desired for the blends of polyvinylchloride used herein. Azodiisobutyronitrile and like catalysts are alsoquite useful.

It is desired to point out that the concept of utilizing r mixtures ofsuspension grade and dispersion grade polyvinyl chloride particlestogether with suflicient reactive plasticizer comprising styrene, vinyltoluene or chlorostyrene to provide an initially fluid mixture intowhich separate fibers can be mixed to provide a tacky paste which can besheeted using rolling pressure to form. the paste into a thin sheetwithout disrupting the incorporated fibers is of importance inmaximizing the proportion of vinyl chloride polymer which can be usedwith reinforcing fibers. This technique is therefore of value regardlessof whether the reactive plasticizers include other vinyl monomers orpolyethylenic monomers. Thus, and where solvent resistance is ofsecondary importance, this technique is of value even in the absence ofa thermosetting cure resulting from the presence of polyfunctionalplasticizer.

The proportion of vinyl chloride polymer can be further increased whenit is recognized that the monoethylenic monomer, and especially styrene,is volatile so that if the sheets used to confine the tacky fiber-filledmass are removed, a proportion of the monoethylenic monomer willevaporate, thus increasing the relative proportion of vinyl chloridepolymer to reactive plasticizer and also increasing the percentage offiber reinforcement.

EXAMPLE 60 parts by weight of polyvinyl chloride resin constituted by anequi-weight mixture of dispersion grade and suspension grade productseach of which are high molecular weight essentially homopolymericpolyvinyl chloride resins are mixed with 40 parts by weight of liquidplasticizer constituted by a /35 weight ratio mixture of 1,3- butyleneglycol dimethacrylate and styrene. The dispersion grade resin has anaverage particle size which permits 100% passage through a 200 meshscreen and the suspension grade resin has an average particle size whichpermits 95% to pass through a 100 mesh screen.

The mixture is of low viscosity as initially formulated and pourable atroom temperature. 1% by weight of tbutyl perbenzoate, based on theweight of plasticizers, is mixed into the plasticizers before the resinparticles are added. The mixture has a work life of many hours (at least4 hours).

Glass fibers in the form of chopped glass roving /2" in length are addedto constitute 28% by weight of the total mixture, 20-35% representingnormal preferred practice.

At this stage, the fiber-containing mixture may be fluid or pastry. Ifthe mixture is too fluid, the application of pressure will cause thefibers to separate from the resin and the mixture is allowed to standuntil it thickens and becomes pasty as indicated by the development of asticky mass which does not flow in the absence of applied pressure. Thispasty mixture is placed between nitrocellulosecoated cellophane sheetsand rolled to form a sheet having a thickness of /3". Of course, thethickness of the sheet can be varied as desired. This sheet is confinedbetween press platens having a temperature of 140 C. for seconds tocause the polymer particles to fuse together and form a non-porousflexible sheet which can be cured using temperatures of 120-200" C. forfrom 1 to 6 minutes, with longer cures permitted.

Typical molding conditions are 150 C. at pressures of from 101000p.s.i., the cure being easily completed in two minutes. The flexiblegelled sheet can be cut up into small squares, e.g., %"-%2" on a sideand molded under the conditions specified with the resin and fiberflowing together to fill the mold and form a unitary product.

Repeating the foregoing, but removing the protective cellophane sheetallows much of the styrene to evaporate and the polyvinyl chloridecontent is increased in the lfinal cured product. By noting the loss inweight of the gelled sheet, the loss of styrene can be readilycontrolled to give a specific formulation. In this example, thepolyvinyl chloride content of the mixture based on the combined weightof the resin and plasticizer was increased from 60% to 75%. Of course,the reduced proportion of 8 plasticizer also results in an increase inthe proportion of glass fiber based on the total weight of the mixture.

Johns Manville glass roving C5308 illustrates a commercially availableglass roving which can be used if desired.

I claim:

1. A pasty mixture in which fillers are uniformly dispersed andconsisting essentially of particles of thermoplastic polyvinyl chloridepolymer dispersed in a liquid reactive plasticizer component, saidpolymer containing at least 96% by weight of vinyl chloride and saidplasticizer component consisting essentially of low molecular weightpolyester reaction product of alpha, beta-ethylenically unsaturatedmonocarboxylic acid with aliphatic polyhydric alcohol having a molecularweight below 600 or unsaturated alcohol esters of monoethyleniccarboxylic acid in admixture with monoethylenic monomer comprisingmonovinyl aromatic monomer, said monoethylenic monomer constituting from20% to 98% of said reactive plasticizer component, and free-radicalgenerating polymerization catalyst distributed in said mixture.

2. A pasty mixture as recited in claim 1 in which said monovinylaromatic monomer is selected from the group consisting of styrene, vinyltoluene, chlorostyrene and mixtures thereof.

3. A pasty mixture as recited in claim 1 having discrete reinforcingfibers dispersed therein.

4. A pasty mixture as recited in claim 1 in which said polymer particlesare constituted by a mixture of dispersion grade polyvinyl chlorideparticles with at least based on the weight of the mixture of particles,of suspension grade polyvinyl chloride particles.

5. A pasty mixture as recited in claim 4 in which said reactiveplasticizer component comprises said polyester reaction product inadmixture with monoethylenic monomer comprising styrene with saidmonoethylenic monomer constituting at least about 50% of said reactiveplasticizer component.

6. A pasty mixture as recited in claim 1 in which the weight ratio ofliquid plasticizer component to said polyvinyl chloride polymer is fromabout /70 up to about 50/150.

7. A pasty mixture as recited in claim 1 in which said pasty mixturecontains at least 5%, based on total weight, of reinforcing fiber.

8. A pasty mixture as recited in claim 5 in which said monoethylenicmonomer further comprises vinyl toluene or chlorostyrene.

9. A pasty mixture as recited in claim 1 in which the weight ratio ofliquid plasticizer component to said polyvinyl chloride polymer is atleast /65 and said polymer particles are constituted by a mixture ofdispersion grade polyvinyl chloride particles with from -60%, based onthe weight of the mixture of particles, of suspension grade polyvinylparticles.

10. A pasty mixture as recited in claim 9 in which said pasty mixturecontains at least 10% by weight, based on total weight, of reinforcingfibers having a fiber length of from /s" to 1".

11. A reactive curable composition comprising the pasty mixture of claim1 in the form of a flexible solid wherein the polyvinyl chlorideparticles are solvated and merged with one another Without significantpolymerization.

12. A flexible solid as recited in claim 11 having the form of a sheet.

13. A flexible solid as recited in claim 12 in which discretereinforcing fibers are dispersed throughout said sheet with a uniformfiber to resin distribution.

14. A flexible solid as recited in claim 12 in which said sheet issubdivided to form discrete pieces having dimensions in the range of /s"to 1".

15. A method of producing a composition adapted to be molded under heatand pressure to produce non-porous molded products comprising forming amixture comprising vinyl chloride polymer particles containing at least96% by Weight of vinyl chloride dispersed in liquid reactive plasticizercomprising styrene, heating said mixture free from exposure to air at anintermediate solvating temperature for a time sufficient to cause saidvinyl chloride particles to flow and merge with one another withouteffecting significant polymerization to thereby form a flexible solidcontaining unpolymerized styrene, and allowing said unpolymerizedstyrene to vaporize from said flexible solid and thereby increase theproportion of said vinyl chloride polymer in the mixture.

16. A method as recited in claim 15 in which said liquid reactiveplasticizer comprises a mixture of styrene and less volatile monovinylaromatic monomer selected from vinyl toluene, chlorostyrene and mixturesthereof.

17. A method of producing a reinforced composition adapted to be moldedunder heat and pressure with the composition flowing to producenon-porous and cured molded products in which the reinforcement isuniformly distributed comprising forming a reinforced mixture comprising(1) a mixture of vinyl chloride polymer particles of dispersion gradeand vinyl chloride polymer particles of suspension grade, said vinylchloride polymers containing at least 96% by weight of vinyl chloride,at least 25% of said vinyl chloride polymer particles being ofsuspension grade, (2) liquid reactive plasticizer comprising monovinylaromatic monomer selected from styrene, vinyl toluene, chlorostyrene andmixtures thereof, (3) free radical polymerization catalyst, and (4)filler, said components (1) and (2) being proportioned to form a fluidmixture upon admixture with one another, and said filler being uniformlydispersed in said mixture, permitting said mixture to stand to causesaid monovinyl monomer to be absorbed or adsorbed into said vinylchloride particles to convert said mixture into a pasty mixture in whichsaid filler will flow with the resinous component of the mixture whenthe same is subjected to pressure, and then applying pressure to saidpasty mixture to form the same into a mass adapted for molding.

18. A method of producing a fiber-reinforced composition adapted to bemolded under heat and pressure with with the composition flowing toproduce non-porous and cured molded products in which the fiberreinforcement is uniformly distributed comprising forming afiber-reinforced mixture comprising (l) a mixture of vinyl chloridepolymer particles of dispersion grade and vinyl chloride polymerparticles of suspension grade, said vinyl chloride polymers containingat least 96% by Weight of vinyl chloride, (2) liquid reactiveplasticizer comprising monovinyl aromatic monomer selected from styrene,vinyl toluene, chlorostyrene and mixtures thereof, (3) free radicalpolymerization catalyst, and (4) discrete reinforcing fibers, saidcomponents (1) and (2) being proportioned to form a fluid mixture uponadmixture with one another, and said discrete fibers being uniformlydispersed in said mixture, permitting said mixture to stand to causesaid monovinyl monomer to be absorbed or adsorbed into said vinylchloride particles to convert said mixture into a pasty mixture in whichsaid discrete reinforcing fibers Will flow with the resinous componentof the mixture when the same is subjected to pressure, and then applyingpressure to said pasty mixture to form the same into a mass adapted formolding.

19. A method as recited in claim 18 in which said pasty mixture isformed into a sheet between protective layers of non-adhesive sheetmaterial.

20. A method as recited in claim 19 in which at least a portion of saidmonovinyl aromatic monomer is styrene and said protective layers ofnon-adhesive sheet material are removed to permit a portion of saidstyrene to evaporate and thereby increase the proportion of vinylchloride polymer in the mixture.

21. A method of producing a fiber-reinforced composition adapted to bemolded under heat and pressure to produce non-porous molded productscomprising forming a fluid mixture comprising as the essential resinouscomponent thereof (1) a mixture of vinyl chloride polymer particles ofdispersion grade and vinyl chloride polymer particles of suspensiongrade, said vinyl chloride polymers containing at least 96% by Weight ofvinyl chloride with said suspension grade particles constituting from40-60% by weight of the mixture with said dispersion grade particles,(2) liquid reactive plasticizer comprising monovinyl aromatic monomerselected from styrene, vinyl toluene, chlorostyrene and mixturesthereof, and (3) free radical polymerization catalyst, mixing into saidfluid mixture materials comprising reinforcing fibers to form a fluidmixture having reinforcing fibers dispersed therein, and then permittingsaid fluid mixture to stand to cause said monovinyl monomer to beabsorbed or adsorbed into said vinyl chloride particles to produce apasty mixture in which said reinforcing fibers will flow with theresinous component of the mixture when the mixture is subjected topressure.

References Cited UNITED STATES PATENTS 2,794,753 6/1957 Duddy 2608843,133,825 5/1964 Rubens 260-884 3,157,713 11/1964 Leese 260 -8843,252,935 5/1966 Thompson et al. 260884 3,275,713 9/1966 Rubens et a1.260 -884 3,275,714 9/1966 Thompson 260-884 FOREIGN PATENTS 293,4371/1964 Netherlands 260884 SAMUEL H. BLECH, Primary Examiner R. J.S-EIBERT, Assistant Examiner U.S. Cl. X.R. 260884, 899

